Implants have long been used in the field of implant dentistry. Dental implants are used to replace individual teeth or as a support structure for anchoring more complex abutment structures, which generally replace several or even all of the teeth. The materials used for the dental implants are often titanium and alloys thereof, and increasingly ceramic materials. These materials have the necessary strength for withstanding the mechanical loads that occur, and they are at the same time sufficiently biocompatible.
The shape and construction of the dental implant depends mainly on the exact purpose for which it is used. The implants are often constructed in two parts, in which case they consist of an anchoring part, often referred to in isolation as the implant, and of a separate abutment. The anchoring part is either embedded completely in the bone, that is to say to the height of the alveolar crest, or protrudes by a few millimeters from the alveolar crest into the soft tissue. The abutment is mounted on the anchoring part either after the latter has become incorporated (osseointegrated) into the bone or directly after the anchoring part has been inserted. It can also be attached to the anchoring part prior to insertion. Ultimately, the desired prosthetic element (e.g. bridge or crown) is connected to the abutment. The prosthetic element can be adhesively bonded, cemented or screwed onto the abutment. It is also possible for the implant to be constructed in one part, such that the anchoring part and the abutment are produced from one piece. Hence in such implant systems the integral anchoring part and abutment are positioned within the mouth at the same time.
One-part implants have good mechanical stability but have disadvantages from an aesthetic point of view. Such implants are currently made in most cases of titanium or a titanium alloy, which is why the visible part of the implant can create an undesired metallic appearance. In addition the abutment shape and angulation, relative to the anchoring part, must be selected prior to insertion. This provides the surgeon with less flexibility and room for error in the placement of the implant.
By contrast, two-part implants are more versatile in use, because the anchoring part and the abutment can be adapted individually to the particular requirements. However, the multi-part structure can have a negative impact on the mechanical stability of the overall implant or the overall structure. An advantage of two-part implants is that the abutment can be made from a different material than the anchoring part, and in this way a surface can be obtained whose colour merges satisfactorily with the surrounding tissue.
In recent times, ceramic materials with sufficient mechanical stability have also become available, such that one-part or two-part dental implants can be produced from ceramic materials.
EP 1 609 436 describes a ceramic implant of this kind. The dental implant is composed of an anchoring part for anchoring in the bone and of an abutment for receiving a prosthetic superstructure. The implant is produced in one piece from a material based on zirconium oxide.
The dental implants known from the prior art and made of a ceramic material or other material have proven difficult to handle. The abutment often has a more or less circular cylindrical shape which, combined with the hard and smooth surface of the ceramic material, makes it difficult to grip. In addition, the abutment section of a one piece implant has to have special structures, e.g. grooves, indents, projections and the like, in order to allow the dental implant to be screwed into the drilled hole provided for it. In conventional abutments, there is also a danger that the prosthetic elements mounted on them will break relatively easily in their apical end area. This is because of the shaping which, in the apical end area of the prosthetic elements, must narrow in diameter and smoothly join to the circumference of the implant. In the end area of the prosthetic element lying on the abutment therefore, fractures may occur in thin-walled areas under mechanical loading. This is a particular problem with ceramic prosthetics, which are brittle and therefore prone to chipping.